Device for heat shrinking film onto an open-topped container

ABSTRACT

A device for heat shrinking thin film onto open-topped containers to form spill-resistant covers is shown. A radiant energy source is intermittently energized in association with timers to direct radiant energy towards the thin film. An energy absorbing body is associated with the thin film to absorb energy and create heat adjacent to the film which in turn causes the thin film to shrink. The energy absorbing body can be the adaptation of the thin film to be opaque to the radiant energy by either being coated with an energy absorbing coating such as printing, or being made partially opaque by means of tinting. The container can also be adapted to absorb energy by including a darkened band adjacent the upper edge of the rim. The device can also interpose an energy absorbing body, such as a darkened aluminum screen adjacent to the film to be heated to cause the thin film to shrink. The device shrinks the thin film around the rim first, then shrinks the film across the top of the container to form a spill-resistant cover. In one embodiment, printed patterns on the film can be used to create perforations.

FIELD OF THE INVENTION

[0001] This invention relates to a device which may be used to seal foodinto open-topped containers. In particular, this invention relates to adevice suitable for heat shrinking film onto such open-topped containersto seal food or drink inside the container.

BACKGROUND OF THE INVENTION

[0002] Presently in the fast food drink industry it is typical to servea drink in a paper, plastic or other disposable cup topped with apreformed plastic lid. The plastic lid fits tightly over the lip formedat the top of, for example, a paper drink cup, and may include aperturesto permit straws or openings to be formed in the lid to directly drinkthe contents of the cup.

[0003] Unfortunately, there are many problems associated with the use ofthese plastic lids. For example, the lids are generally expensive.Further, the lids are bulky and create problems in storage and indisposal. Further, the seal formed by the lids is dependant upon the lidbeing placed on properly, and can leak if not properly placed. Finally,the handling of the lid is not completely hygienic.

[0004] In order to overcome these problems, various devices and methodshave been proposed in which a cover is placed on an open-toppedcontainer and then heated to shrink it into sealing engagement with thetop of such a container. Examples of such devices can be found in thefollowing United States patents: U.S. Pat. Nos. 3,260,775; 3,354,604;3,460,317 3,491,510; 3,494,098; 3,507,093; 3,621,637; 3,877,200;3,838,550; 3,916,602; 4,035,987; 4,184,310 and 4,562,688. While thesolutions proposed by these prior devices and methods are interesting,they fail to provide a sufficiently cost efficient, easy and inexpensivealternative to preformed rigid plastic lids. As a consequence, rigidplastic lids remain in widespread use. Some of the main failings ofthese prior devices are that they are bulky, noisy, unresponsive, andexpensive. Heating systems comprising blowing air over a hot element andthen onto a film require large amounts of unnecessary heat, even when instandby mode, which makes temperature control very difficult. Further,continuous elevated temperatures are expensive to maintain and may bedeleterious to the immediate environment.

SUMMARY OF THE INVENTION

[0005] Aside from the benefits of increased hygiene and reduced waste,the present invention is directed to providing a practical device whichhas commercial utility. One aspect of the present device is to providean energy efficient way of sealing open-topped containers which avoidsany substantial build-up of heat. An intermittent source of radiantenergy is used, and energy is directed onto an energy absorber locatedat the specific place where heat is required. Thus, heat is originatedwhere it is needed, when it is needed and a cooler, quieter, safer andmore efficient device results.

[0006] The present invention provides a device for heat shrinking acover onto an open-topped container, said device comprising:

[0007] a housing adapted to receive said container; and having a stripof heat shrinkable thin film;

[0008] a cutting means positioned against said thin film for cuttingsaid thin film upon said thin film being urged onto said cutting meansby said container;

[0009] a hood for holding a cut piece of said film in place across saidopen top of said container, wherein said cut piece includes a portionextending from under said hood downwardly around an upper outer rim ofsaid container;

[0010] a first radiant energy source for directing energy toward saiddownwardly extending portion of said cut piece of film;

[0011] a first means to absorb radiant energy to transfer heat to saiddownwardly extending portion of said cut piece of film; and

[0012] a switch means for intermittently energizing said first radiantenergy source whereby said downwardly extending portion of said cutpiece of film is shrunk onto said rim;

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a device according to the presentinvention in use;

[0014]FIG. 2 is a front sectional view of an open-topped containeraccording to the present invention with a heat shrunk cover in place;

[0015]FIG. 2a is a top view of the container of FIG. 2.

[0016]FIG. 3 is a front view of the container of FIG. 2 having adarkened upper band;

[0017]FIG. 4 is a top view of the device of FIG. 1, with the top wallbroken away to show the contents;

[0018]FIG. 5 is a sectional view taken along lines 5-5 of FIG. 4;

[0019]FIG. 6 is a view similar to FIG. 5 with the container in a raisedposition;

[0020]FIG. 7 is a view of a part of the device of FIG. 1; and

[0021]FIG. 8 is a view along lines 8-8 of FIG. 7;

[0022]FIG. 9 is an alternate configuration for a knife element shown inFIG. 5;

[0023]FIG. 10 is a view along lines 10-10 of FIG. 9;

[0024]FIG. 11 is a schematic sketch of an electronic control circuit forthe present invention;

[0025]FIG. 12 is an alternate embodiment of a micro-switch systemaccording to the present invention;

[0026]FIG. 13a is a view along lines 13-13 of FIG. 12 in a firstposition; and

[0027]FIG. 13b is a view along lines 13-13 of FIG. 12 in a secondposition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028]FIG. 1 shows a device 10 for heat shrinking a thin film onto anopen-topped container 12. The housing 10 includes an opening 14 ofsufficient size to allow placement of the container 12 within thehousing 10. In the embodiment of FIG. 1, placement of the container 12within the opening 14 is accomplished manually, illustrated by a hand16.

[0029] Turning to FIG. 5, there is shown a cross-sectional schematicview of the operational components of the device 10 of FIG. 1. Thecontainer 12 is shown in the opening 14. The opening 14 is defined byside walls 18 and 20 of the device 10. Shown on the right-hand side is aroll of thin plastic film 22 on an axle 24. The film 26 passes over aroller 28 across the top of the container 12 across a second roller 30and onto a take-up axle 32. Shown at 34 is a rewind motor. It will beappreciated that the rewind motor 34 can rotate the pick-up axle 32 inthe direction of arrow 36 which will advance the film 26 across the topof the container 12 and cause the roll of film 22 to rotate in thedirection of arrow 38. Alternatively, the advancing of the film 26 couldbe accomplished manually by turning a lever or knob mounted on take-upaxle 32.

[0030] The film 26 is preferably a bi-axially oriented shrink filmhaving a preferred thickness of between 60 to 100 gauge. Good resultshave been achieved with a 75 gauge polyvinyl chloride film purchasedfrom Reynolds Metals Company at Richmond, Va. Other films, such ascopolymers, polyolefins and the like may also be appropriate. The film,to be most useful, must be foodgrade contact-approved by the appropriateregulatory authorities. A 7½″ outer diameter roll of 75 gauge shrinkfilm, which includes a 3″ diameter fibre core, will yield approximately8,000 covers according to the present invention.

[0031] In FIG. 5, the container 12 is located in a locator identifiedgenerally at 40. The locator 40 is shown in more detail in FIGS. 7 and8. Turning to FIG. 7, there is shown a plate 42 having a pair opposedguides 44 and 46. The plate 42 also has an opening 48 located betweenthe guides 44, 46. The guides 44 and 46 are substantially identical andtherefore the following discussion in respect of guide 44 appliesequally to guide 46.

[0032] The guide 44 comprises a rub rail 50 which contacts an outer edgeof a container 12. Extending from plate 42 are two posts in respect ofeach guide 44, 46. In respect of guide 44 there is a stop post 52 and aguide post 54. A slot 56 is formed in the guide 44 and a spring 58 ishoused between the guide post 54 and the end of the slot 56. A pin 59may be used to secure one end of the spring 58. A washer 60 is used toretain the other end of the spring 58 within the slot 56. The washer 60is placed around the guide post 54. Between the free end 55 of guidepost 54 and the washer 60 is a further spring 61. The spring 61 allowsthe guide plate 44 to articulate away from the plate 42 to facilitateremoval of the container 12 from the device 10.

[0033] It will now be appreciated that the guide 44 can move laterallyin the direction of double ended arrow 62 guided by means of the stop 52and the guide post 54 with the slot 56. It will also be appreciated thatthe curved portion 64 of the rub rail 50 will provide an indication toanyone inserting a container 12 into the locator that the container isappropriately located. Appropriately in this sense means centered underthe plate opening 48.

[0034] Turning to FIG. 8, the locator 40 of FIG. 7 is shown incross-sectional view. As can be seen, the guides 44 and 46 arepositioned on adjacent side edges of a container 12. The plate opening48 is shown together with the plate 42. The thin film 26 is also shownstretched across the top 13 of the container 12.

[0035] It can now be appreciated that the container 12 can be moved inthe direction of double ended arrow 64 into position beneath plateopening 48. During this period, the guides 44 and 46 will gradually openand then close about the periphery of the container 12. Thereafter, asshown in FIG. 8, the container 12 is free to be moved in the directionof double ended arrows 66 as will be discussed below. It will beappreciated that containers 12 of varying diameter can thus beaccommodated by the instant invention, since all containers will becentered by the locator beneath the plate opening 48. This is desirablein a food services environment where cup size selections typicallyinclude small, medium and large.

[0036] Turning now to FIG. 5, a container 12 is shown centered inlocator 40. A first radiant energy source 68 and a second radiant heater70 can now be explained. Located above the centered and locatedcontainer 12 is a top shrink hood 72. The second radiant heater 70 islocated within the top shrink hood 72. The top shrink hood 72 includes aglass shield 74 and a heat transfer means 76. In some circumstances theglass shield 74 may not be required, however, to prevent the possibilityof splashes reaching the second radiant energy source 70, it ispreferred. It may not be necessary to use glass. Plastic or othertransparent substances may be appropriate. Good results have beenachieved when the heat transfer means 76 is made from a screen aluminummaterial painted a dark colour, such as black. The dark aluminum heatsand cools quickly which is desirable in the circumstances.

[0037] A pierce tool 78 is also shown extending outwardly from the heattransfer means 76. The purpose of the pierce tool 78 is to make a ventopening in the thin film to allow gases such as carbon dioxide from asoft drink to escape the container.

[0038] An alternative to pierce tool 78 is to form small opaque portions79 in the shrink film. These opaque portions or “dots” will cause a hotpoint which may perforate the film as more fully explained below. Ifdesired the hot points can be made in a specified pattern to form asipping opening or the like, as shown in FIG. 2A. Also shown in FIG. 2is a straw 122 with a pointed end 124 for piercing the film, shown inplace as 126. A fluid, such as a soft drink is shown at 128.

[0039] Also shown in FIG. 5 is a drive belt 80 which connects a pulley82 with a motor. Attached to the pulley 82 are a pair of arms 84. Thearms 84 rotate when the pulley 82 is rotated by the belt 80. Dependingfrom the arms 84 about pivot points 86 are pivot arms 88. Pivot arms 88include a roller 90 at one end and the first radiant energy source 68 atthe other end. If preferred, a reflector may be provided such as 92around the first radiant energy source 68.

[0040] Also show in FIG. 5 is a knife or film cutting blade 94 to whichis attached a heating element 96. The heated blade 94 ensures a quickclean cut of the thin film, upon the thin film contacting the blade 94.As can be seen from FIG. 5, the blade 94 is below the top hood 72, sothe film will be cut to shape just prior to or about the same time asthe container 12 contacts the hood 72. Good results have been achievedwhen the blade is made from a two point center face steel cutting rule,and maintained at a temperature of between 275° F. to 400° F. Thisformat appears to limit smoke and fume generation.

[0041] The knife 94 may be circular in shape, or may be as shown inFIGS. 9 and 10. It will be noted that the knife 94 in FIGS. 9 and 10includes a rounded oblong section 95. This will result in a similarlyshaped section being formed in a cut piece of film, as described below,which can be used as a convenient pull tab for removing a cover whichhas been shrunk onto a container 12. In the preferred embodiment thethin film 26 has a width greater than the width of the knife 94 so thata trim 27 (see FIG. 5) is left after the cut is made, and the trim 27 isstrong enough to allow the film 26 to be advanced by a tensile forcewithout tearing.

[0042] Turning now to FIG. 6, the operation of an instant device can nowbe understood. In FIG. 6 the container 12 has been raised in thedirection of arrow 100. This has had the effect of pushing the film 26upwardly into engagement with the knife heated film cutter blade 94.This has caused a cut portion of the film shown as 102 to be drapedacross the top 13 of the container 12. At this point the hood 72 isholding the cut piece of film 102 generally in place. As the container12 is raised further, the hood 72 is also raised. Rollers 90 thencontact a ledge 104 formed on the outer surface of the hood 72. Furtherupward movement causes the movement of the first radiant energy source68 about the pivot point 86 until the first radiant energy source 68 isclosely adjacent to a draped over edge of cut portion 102 shown as 103.Contact is then made at a limit switch, as explained below in respect ofFIG. 11, which energizes a motor 99 (shown in FIG. 4). Upon energizationof the motor 99, the belt 80 revolves causing the rotating arms 84 torevolve rotating the first radiant energy source 68 about the peripheryof the top of the container 13. Simultaneously with the energization ofthe motor 99 and the rotation of the first radiant energy source 68, thefirst radiant energy source 68 is energized to cause radiant energy tobe directed towards the dangling edge 103 of the cut portion 102 of thesaid film 26.

[0043] It will be appreciated that the preferred invention causes thefirst radiant energy source 68 to move into position closely adjacentthe downward edge 103 of the cut portion 102. Such movement is preferredbecause radiant energy obeys the inverse squared rule in which theamount of energy is proportional to an inverse of the square of thedistance from the source. By locating the first radiant energy source 68close prior to being energized, more energy can be usefully used andfocused away, for example, from an operator's hands. Also, by thepivoting action, the operator's hands are kept clear of the energysource 68, until the container 12 is in position.

[0044] After a predetermined length of time, the first radiant energysource 68 is de-energized and the second radiant energy source 70 isenergized by a timer 120. The second radiant energy source 70 energy isdirected through the glass shield 74 onto an energy absorbing body 76.This transfer of heat causes a shrinking of the top portion acrosscontainer 12 of the cut portion 102. Thereafter, the sealed container 12can be lowered and removed from the apparatus.

[0045] A preferred type of energy absorbing body 76 is a darkenedaluminum screen. The body 76 is placed very closely adjacent the topportion of the cut section 102 and may be in contact therewith. Thedarkened screen or body 76 absorbs energy and transfers it onto the topportion. It will be appreciated that aluminum is a suitable materialbecause it will cool rapidly, when the energy source 70 is shut off,thereby preventing premature shrinkage of a top portion on a subsequentcontainer upon being first introduced into the hood 20.

[0046] It has been found that the preferred radiant energy sources areTungsten Halogen Lamps. About 70% of the energy produced by these lampsis in the preferred wavelength range of the infrared (750 millimicronsand beyond).

[0047] These lamps are compact, durable, inexpensive and readilyavailable. Lamps in the range of 200 to 300 watts are suitable. It willbe appreciated by those skilled in the art that other energy sourceswhich produce sufficient infrared radiant energy may also be used.

[0048] It is also to be noted that the radiant energy emitted by such anenergy source can be turned on and off instantaneously and focused anddirected to the location it is desired, without stray heat energy beingproduced, and the energy source does not have to be on continuously, oron standby in readiness for a container, which is the case of prior arthot air systems.

[0049] Turning now to FIG. 4, the belt 80, pulley 82 and drive motor 99are all shown. Also are shown two rotating arms 84 and two first radiantheaters 68. It will be appreciated by those skilled in the art thatfewer or more radiant heating elements could be used according to spacerequirements and preference. However, when the drive motor operates at100 rpm, two radiant heat means 68 provides good results. By varying thesize of the pulley 82, the speed of revolution of the first radiantenergy source 68 can also be varied. Good results have been achievedwhen the pully 82 is configured to cause the first radiant energy source68 to rotate at 100 rpm.

[0050] It will also be appreciated that the spinning first radiantenergy source 68 could be replaced with a row of fixed position bulbs.However, the process would be slightly more difficult to control, sincethe total energy output would likely be greater, and more energyexpensive. Thus, the moving first energy source 68 is preferred.

[0051] Turning to FIG. 11, a schematic of an electrical system 150 forthe instant invention is disclosed, which sets out in more detail theinteraction between the container 12 and hood 72 location, and theactivation of the various components described above.

[0052] One of the characteristics of the electrical design is that itmust compensate for the varying rates that the container 12, which ismoved by a human hand, enters and leaves the device 10.

[0053] In the preferred embodiment the raising and lowering of hood 72and the motion of locator 40 will trigger micro-switches which engagetimers as described below. Certain events must take place as hood 72 israised and other events must take place when hood 72 is lowered.

[0054] Referring to the wiring system 150, F1 is a fuse. When the mainswitch 170 is turned on, a pilot light R lights up. Then, switches S1and S2 are manually turned on. As shown, S1 turns on resistance heater96, which heat the knife 94. A thermostatic control is shown at 97. WhenS2 is turned on, it activates motor 99 and also signals timer T1. Alsoshown is a relay TM-1. The timer T1 engages motor 34 and advances thefilm 26 for a single “space”, which is determined by the time set ontimer T1. Thus when the machine is activated and ready to operate byturning on switch S2, a fresh piece of film 26 is automaticallypresented. Switch LS1 is situated on plate 42, (shown in ghost outlinein FIG. 7) so that when guide 46 rotates outwardly on withdrawal of thecontainer, LS1 also signals timer T1 which engages motor 34 and advancesthe film in a like manner.

[0055] Also shown are switches LS2 and LS3 which close when hood 72moves upward. These switches activate a second timer T2 which activatesrelay TM-2 which in turn activates first radiant energy source 68. Onthe downward motion switch LS3 opens and thereby prevents timer T2 fromactivating source 68 again.

[0056] On the downward motion of hood 72, switch LS4 closes, whichactivates timer T3 which through a relay TM-3, activates radiant energysource 70 for a predetermined time.

[0057]FIG. 12 shows in schematic form the microswitch interconnections.On the left hand side of FIG. 12 are the belt 80 around the pulley 82. Ashaft 200 extends upwardly from the top hood 72. A connecting rod 202 isattached to shaft 200, and will rise and subside with the hood 72 beingraised and lowered. Remote from shaft 200 there is a rack 204 connectedto the rod 202 which interacts with a pinion 206, in a manner shown bydouble ended arrows 208. Also shown are a cam shaft 210 attached toeccentric cams 212.

[0058] Shown in FIGS. 13A and 13B are the means of closing electricalcircuits upon rotation of the cam shaft 210 by the pinion 206. Asecondary roller 214 is located on a pivot arm 216. When cam 212 isrotated in one direction an electrical spring clip 218 is forced intocontact with an electrical contact 220 closing a circuit. Upon beingrotated in an opposite direction, the cam 212 urges the pivot arm 216 upand out of the way, and does not close the circuit, as shown in FIG.13B.

[0059] It can now be appreciated that the present invention uses radiantenergy from the radiant energy sources to effect shrinkage. Radiantenergy is preferred, because it travels relatively unimpeded throughtransparent mediums such as air or transparent film. The preferredradiant energy source is a Tungsten-Halogen bulb, which is described inmore detail above. The present invention has process parameters forheating which depend upon an absorbing means for the radiant energy, andin particular, how close any absorbing means conforms to a theoreticallyideal “black body”. An ideal “black body” completely absorbs all radiantenergy that strikes it and thus is capable of radiating that same energyoutward.

[0060] The way in which the present invention seals heat shrinkable thinfilm onto a container, is to employ a first means to transfer heat tothe downwardly extending portion of the cut piece of thin film. In thissense, the first means can comprise adapting the thin film to absorbenergy, interposing an absorbent body adjacent to thin film, or adaptingthe area of the container just below the rim to become energy absorbing.The thin film can be adapted to absorb energy by being made from atinted material, or by being coated with an energy absorbent coating,for example, printing. The ability of the opaque or coated film toabsorb radiant energy will vary depending upon what type of tinting orcoating is used. A darker or more opaque film will absorb more energy.

[0061] An example of a preferred interposed absorbent body is a darkenedaluminum screen 112, which moves closely adjacent the edge 103. Thedarkened portion of the screen will absorb energy and then radiate it,giving rise to heat. The heat will be transferred to the air adjacent tothe film, then to the film which will shrink the film.

[0062] The container may be adapted to absorb radiant energy, and thusproduce heat in a preferred location, by including a darkened band 15 inthe area where heat generation is desired, such as just below the rim.For aesthetic reasons, black bands may not be acceptable, but othercoloured bands will also work. With a cooler colour, the exposure to theradiant energy source may need to be slightly longer. However, thelength of time of exposure to the radiant energy source can be adjustedin the present invention through adjustments made to the timer T2. A gap17 may be incorporated into the band 15 to permit the end user to liftthe shrunken cover off the container if so desired.

[0063] In some circumstances, it may be desirable to urge the film ontothe cup. Therefore, the present invention also comprehends the use of aspring wire 110, which trails (or leads) the revolving first radiantheat means 68, and urges the edge 103 into contact with the container 12just below the top 13.

[0064] It will be appreciated by those skilled in the art that theforegoing description relates to a preferred embodiment and that variousmodifications can be made without departing from the broad scope of theappended claims. Some of these modifications have been discussed aboveand others will be apparent to those skilled in the art.

We claim:
 1. A device for heat shrinking a cover onto an open-toppedcontainer, said device comprising: a housing adapted to receive saidcontainer; and having a strip of heat shrinkable thin film; a cuttingmeans positioned adjacent said thin film for cutting said thin film uponsaid thin film being urged onto said cutting means by said container; ahood for holding a cut piece of said film in place across said open topof said container, wherein said cut piece includes a portion extendingfrom under said hood downwardly around an upper outer rim of saidcontainer; a first radiant energy source for directing energy towardsaid downwardly extending portion of said cut piece of film; a firstmeans to absorb radiant energy to transfer heat to said downwardlyextending portion of said cut piece of film; and a switch means forintermittently energizing said first radiant energy source whereby saiddownwardly extending portion of said cut piece of film is shrunk ontosaid rim;
 2. A device as claimed in claim 1 further including a timermeans for de-energizing said first radiant energy source after apredetermined time and for energizing a second radiant energy sourcelocated in said hood; said second radiant energy source directing energyonto a second means to absorb radiant energy, to transfer heat to thethin film across the top of the container; whereby said cut piece offilm is shrunk across the top of said container after being shrunkaround the rim of said container to form a spill resistant cover.
 3. Adevice as claimed in claim 1 wherein said first means to transfer heatto said downwardly extending portion of said cut piece of film comprisesadapting said film to absorb at least some of said radiant energy.
 4. Adevice as claimed in claim 3 wherein said film is adapted by being madeat least partially opaque to said radiant energy, and upon being exposedto said radiant energy said opaque film heats up.
 5. A device accordingto claim 4 wherein said thin film is made at least partially opaque bybeing tinted.
 6. A device according to claim 4 wherein said thin film ismade at least partially opaque by being coated with an energy absorbingcoating.
 7. A device as claimed in claim 1 wherein said first means totransfer heat to said downwardly extending portion of said cut piece offilm comprises mounting an energy absorbent body adjacent to said thinfilm.
 8. A device as claimed in claim 7 in which said energy absorbingbody comprises a darkened aluminum screen.
 9. A device as claimed inclaim 1 in combination with a container, and wherein said first means totransfer heat to said downwardly extending portion of said cut piece offilm comprises adapting said container to absorb said radiant energyadjacent said downwardly extending portion.
 10. A device as claimed inclaim 9 wherein said container is adapted by having an energy absorbentband located below an upper rim thereof.
 11. A device as claimed inclaims 3, 7 or 9 wherein said housing includes a dispensing reel and atake-up reel for a continuous strip of said thin film.
 12. A deviceaccording to claim 11 wherein said thin film is a biaxial film ofbetween 40 to 120 gauge thickness.
 13. A device according to claim 12wherein said thin film has a width greater than the width of said knifeto form a trim after said cut portion is made, said trim beingsufficient to allow said film to be advanced by a tensile force in saidtrim without tearing.
 14. A device according to claims 3, 7 or 9 furtherincluding a locator which comprises at least one guide plate.
 15. Adevice according to claim 14 wherein said locator comprises an opposedpair of guide plates, at least one of which is spring loaded.
 16. Adevice according to claim 14 wherein said locator comprises an opposedpair of spring loaded guide plates having curved container contactingsurfaces for centering the container.
 17. A device according to claims3, 7 or 9 wherein said knife means comprises a heated steel rule.
 18. Adevice according to claim 17 wherein said knife means defines a cutpiece of thin film having a symmetrical overhang around all edges ofsaid container.
 19. A device according to claim 17 wherein said knife isheated by a resistance heater to a temperature of between 275° F. and400° F.
 20. A device according to claims 3, 7 or 9 wherein said hoodcovers said top film to prevent said top film from being directlyexposed to energy from said first radiant energy source.
 21. A deviceaccording to claim 2 wherein said second means to absorb radiant energycomprises means to render said film at least partially opaque to radiantenergy from said second radiant energy means.
 22. A device as claimed inclaim 21 wherein said thin film is tinted to absorb energy from saidsecond radiant energy source.
 23. A device as claimed in claim 21wherein said thin film is printed to absorb energy from said secondradiant energy source.
 24. A device according to claim 2 wherein saidsecond means to absorb radiant energy comprises a darkened aluminumscreen.
 25. A device according to claim 2 further including a piercingtool to make at least one hole in said cut piece of thin film.
 26. Adevice as claimed in claim 21 wherein said film includes a pattern ofdiscrete opaque dots forming a predetermined pattern to causeperforations upon exposure to said second radiant energy means.
 27. Adevice according to claim 1 further including a motor, a drive meansconnecting said motor to said first radiant energy source and whereinsaid switch means energizes said motor as well as said first radiantenergy source, and said first radiant energy source is rotated aroundsaid rim.
 28. A device according to claim 27 wherein said first radiantenergy source is pivotally mounted on an arm, and said hood isdisplaceable, and on displacement of said hood, said arm is pivotedabout a pivot point to cause said first radiant energy source to bepositioned adjacent said downwardly extending portion of said cut pieceof thin film.
 29. A device according to claim 28 in which said top hoodfurther includes a ledge, and said arm further includes a roller whichrolls along said ledge upon rotation of said first radiant energysource.
 30. A device according to claim 27 when said first radiantenergy source rotates at about 100 rpm.
 31. A device according to claim28 wherein said arm further includes a means for urging said portion ofsaid film into contact with said rim.
 32. A device as claimed in claim10 wherein said energy absorbent band has at least one gap formedtherein, to facilitate removal of a shrunk piece of film from saidcontainer.
 33. A device as claimed in claim 1 wherein said switch meanscomprises at least one contact operated limit switch.
 34. A device asclaimed in claim 2 wherein said timer means allows said first radiantenergy source to be energized for at least one full revolution.
 35. Adevice as claimed in claim 34 wherein said device includes at least twofirst radiant energy sources and said timer means allows said two firstradiant energy sources to be energized for at least one half revolution.